Transmitter final with series-tuned self-neutralized tank circuit



July 5, 1960 G. c. ROBINSON ETAL 2,944,221

TRANSMITTER FINAL WITH SERIES-TUNED SELF-NEUTRALIZED TANK CIRCUIT Filed May 15, 1959 2 Sheets-Sheet '1 l4 PLATE TERMINAL OUTPUT LINK , INSULATION 2O SHIELDING 40 6 RING l 1 NEUTRAUZING l8 2O BAND 29 Hi M H 36 INVENTORS.

GILBERT G. ROBINSON JAMES H. MADDEN gm-kw RNEYS.

July 5, 1960 c; G. ROBINSON ETAL 2,944,221

TRANSMITTER FINAL WITH SERIES-TUNED I SELF-NEUTRALIZED TANK CIRCUIT Filed May 15, 1959 2 Sheets-Sheet 2 OUTPUT INPUT TUBE CONTROL GRID TO TUBE PLATE CAPACITANCE i I2 I l SHIELDING RING TO I NEUTRALIZING BAND AP CITANCE 26 i 46 c A l l [H L l\ n METAL TUBE RING To TUBE CONTROL GRID CAPACITANCE ,T

38 4O SHIELDING mus TO 4 GROUND INDUCTANCE INVENTORS.

GILBERT G. ROBINSON JAMES H. MADDEN AT ORNEYS.

M. a. a.

United States Patent ice 2,944,221 mmsnmnmn-nmnr; wrrn: SERIES-TUNED TANK. crncurr Gilbert ,6. Robinson, 1302A Smi'tli- Road, China Lake,

'C'iflifi, and James H. Madden, 2666" Chassella Way,.

" Gordbva, can.

Filed May 15, 1959, Ser. No. 813,607

s" Claims. c1: 330-65)- (granted under Title '35; U.S2 Code (1952), see. 266) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to transmitters and particularly to a high powered, low weight and volume transmitter for space vehicle applications.

The transmitter of the present invention uses a seriestuned tank coil wrapped coaxially around the envelope of the final amplifier tube. One end of the tank coil being attached directly to the plate terminal of the tube and the opposite end being attached to a neutralizing band which is insulated from the metal base ring of the tube; tuning being accomplished by a variable capacitor between the metal band and ground. There is no previous method available to provide the power, weight and size requirements obtained by the series-tuned, self-neutralized tank circuit of the transmitter of the present invention.

An object of the invention, therefore, is to provide a high powered, low weight and size transmitter for space vehicle applications.

Another object of the invention is to provide a transmitter final having a series-tuned, self-neutralized tank circuit.

A further object of the invention is to provide an extremely efiicient transmitter of low weight and volume.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a perspective view of a transmitter of the present invention;

Fig. 2 is a circuit diagram of the transmitter of the present invention;

Fig. 3 is a schematic representation of the circuit of Fig. 2 showing interelectrode capacitance, shielding ring to neutralizing band capacitance, and shielding ring to ground.

Referring now to the drawing like numerals refer to like parts in each of the figures.

The transmitter of the present invention comprises a final amplifier tube 10, which is shown as a tetrode in the embodiment described herein, having a series-tuned tank coil 12 wrapped coaxially around the envelope thereof. One end of tank coil 12 is attached directly to plate terminal 14 of tube plate 15; the opposite end of tank coil 12 is attached to a neutralizing band 16 which is insulated from the metal shielding ring 18 of base 19 of tube by means of an insulative separator 20, made of Teflon for example. If the transmitter tube used does not include a shielding ring at the base thereof, a shielding ring may be added thereto and should be grounded only at the cathode pin of the tube. In Fig. 2 neutralizing band 16 is represented as one side of a capacitor and shielding ring 18 is represented as the other side of the capacitor; shielding ring 18 is not shown in Fig. l.

input link 22' is connected between input terminal 23 and ground. Grid coil 25 has one end thereof connected to the control grid 26 of tube 10 and the other end 'thereof connectedto one end of resistor 27 (15K for example) and one" end of capacitor 29 (.002- f. for example). The other ends of resistor 27 and capacitor 29 are connected to ground. Cathode 3th of the tube is connected to ground and to shielding ring 158 Screen grid 32 is connected" to one end of capacitor 34' (.001'" ufi for example), the other end of the capacitor being connectedto' ground; Cathode 30 is also connected to oneend ofcapacitor'36 (.001 of. for example), the other end thereof being connected to the end ofRF choke coil 38', the: other end of choke coil 38 being connected toneutralizihg band 16. Variable tuning; capacitor 40 is connected between neutralizing band 16 and ground. Output link 42 is wrapped coaxially around the envelope of tube 10 at the cold point or point of maximum current of tank coil 12 and is connected between output terminal 44 and ground.

The capacitance between neutralizing band 16 and shielding ring 18 on the base of tube 10 (represented as capacitance 46 in Fig. 3) is made of such value that, considering the phase difference between the neutralizing band and tube plate 15, neutralization is obtained. In other words, to neutralize the system the neutralizing band 16 is made large enough to provide sufiicient capacitance such that, when the capacity is divided between metal shielding ring 18 to tube control grid 26 capacitance and the metal shielding ring to ground inductance (represented as 48 in Fig. 3), the remainder of the capacitance is equal to the tube control grid to plate capacitance. For example, for a 21-326 tube, the neutralizing band to tube shielding ring capacitance is 50 not.

. to neutralize a tube control grid to tube plate capacitance of 0.2 ,uuf.

Plate potential, E is provided through RF choke 38, to neutralizing band 16. Tuning is accomplished by variable capacitor 40 between neutralizing band 16 and ground, and RF energy is removed from the transmitter through output link 42 about the tube envelope.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that Within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In an extremely efiicient transmitter final circuit, a final amplifier tube having an envelope and base and at least a plate and a cathode therein, and a metal shielding ring about the tube base, a series-tuned tank coil wrapped coaxially around the envelope of said tube, one end of said tank coil being attached to the plate of said tube and the opposite end of said tank coil being attached to a metal neutralizing band, said neutralizing band being positioned around and insulated from said shielding ring, a tuning capacitor connected between said neutralizing band and ground, plate potential being provided to the circuit through an RF choke connected to said neutralizing band, RF energy from the circuit being removed through an output link also wrapped coaxially around the envelope of said tube.

2. In an extremely efficient transmitter final circuit, a final amplifier tube having an envelope and base and at least a plate and a cathode therein, a metal shielding ring about the base of said tube and grounded to the cathode thereof, a series-tuned tank coil wrapped coaxially around the envelope of said tube, one end of said tank coil being attached to the plate of said tube and the opposite end of said tank coil being attached to a metal neutralizing band, said neutralizing band being positioned around and insulated from said shielding ring, a" tuning f capacitor connected between said neutralizing band and ground, plate potential being provided through an RF choke to said neutralizing band, RF energy from the circuitbeing rernoved through an output link wrapped coartiall-y around the envelope ofi saidv tube at. the point of maximum current of saidtank coil. j j I V "3. In an extremely' efiicient transmitter final circuit, a final amplifier'tube having an envelope and base and at least a plate, a gridanda cathode therein, a metal shielding ring about the base of said tube and grounded to the cathode thereof, a series-tuned tank cq il wrapped coaxially around the envelope of said tube, one end of said tankcoil being attached to the plate of said tube and the opposite end of said tank coil being attached to a metal neutralizing band, said neutralizing band being positioned around and insulated from said'shieldingring, a tuning capacitor connected between said neutralizing band and ground, plate potential being provided through an RF choke coil to said neutralizing band, RF energy from the circuit being removed "through an' also wrapped coaxially around the envelope of said tube,

said circuit operable to be neutralized by using aneu tralizing band of such size as t0 provide suflicient capacitance that when the capacitance is divided between the shielding ring to tube giidcapacitance and the shielding ring to ground inductance the remainder of the capacitance is equal to the tube grid to tube plate capacitance.

4. A circuit as in claim 3 wherein s'aidtuningcapacitance is a variable capacitance.

5. A circuit as in clai n 3 wherein said: is wrapped coaxially around the envelope-tot. said tube at the point of maximum current of said tank coil.

References Cited in the file of this patent UNITED STATES PATENTS 1,986,805 Liebhart et al. an; 5,1535

2,279,543 Wheeler Apr. 14,,1 942 

